Hello all. I inquired with White Labs and Wyeast. Got no reply from Wyeast, but within several hours White Labs came back with exactly the information we needed for beer:
I presented your question to the head of our Lab Operations and to her knowledge there are no spices that we are aware of that would kill the yeast. You should not have any problems.
White Labs, Inc.
That means we are fine for fermentation. Head retention can be impacted by some spices though; that's a well-known factor.
As for bread baking I have added a huge variety of spices to breads. I generally use an easy and light French bread recipe first to gauge the impact of taste, scent, etc of varying amounts of spices, much as we do when trying spices in beer. In baking I've encountered problems adding garlic, chili peppers, citrus juices, wine, beer, whisky, liquors, and chocolate in bar form to bread dough. In each case the dough did not rise sufficiently. I've doubled the yeast and tried again, but this has not been successful because I suppose the spice or ingredient has altered either the pH or the sugar enough to make the dough inhospitable to the yeast. To use the spices I've waited until after the rise then added them before the bake, either by rolling out the dough and shaking them on or simply pounding them in. Rather than citrus juice I use the zest of several fruits (use a grater and grate off just the colorful part of the outside of the peel - that's the zest). For beers and other liquors reduce them in a warm pot, add margarine and a complimentary spice to make a creamy liquor syrup, then spread this over rolled out dough with a spatula. Roll up and put in the baking pan. Put some more over the top. Bake this and your place is going to smell as close to heaven as it does on days 2 and 3 when your primary fermenter is bubbling away.
Experiment with homebrew syrups and homebrew bread. Sandwiches made with this bread will make your lunch guests redefine good. And your girlfriend/wife/SO/breakfast customers will be begging you for French toast (homebrew syrups AND homebrew bread).